Everything is managed using NotificationCompat API. If an app has standard notifications they will appear in the watch, and all the buttons in the notification will be available in the watch.

Everything in the watch has to be pro-active, besides apps that can register to a closed set of voice intents.

It has a few of interesting tweaks to notifications:
1. You can add a button to a notification that sends voice2text into the app.
2. You can stack multiple notifications.
3. Notifications can have pages for added data.
4. Notifications can have an image background.